The present invention relates to a color image forming method whereby deep images which have a superior color tone can be obtained.
When the conventional eletrophotographic method is used to form color images, there is a method available that image data for each color, which is obtained, for example, by reading a document by a color CCD and performing image processing and color correction, is created on a photo conductor using an inorganic photo conductive material such as ZnO, CdS, Se, or amorphous silicon or a photo conductor using an organic photo conductive material such as phtalocyanine pigment, bis-azo pigment, or polycyclic quinone pigment, an electrostatic latent image is formed for each color by irradiating a laser beam which is modulated by the above image data, the latent image is developed by a color toner, for example, yellow (Y), magenta (M), cyan (C), or black (BK), the color toner image, whenever it is formed, is transferred to a transfer material so as to form a color toner image on the transfer material, and the image is fixed by heating so as to form a color image.
There is an another method available that color toner images are superimposed on a photo conductor so as to form color toner images, and the color toner images are transferred to a transfer material in a batch and fixed so as to form a color image.
Each of the above color toners comprises particles 1 to 20 .mu.m in diameter which are obtained by dispersing a pigment as a coloring agent in a binder resin. The above color toner images are formed by color toner particles which are at least partially overlapped and at least a part of color toner particles are melted by heating, and fused and fixed.
The following can be used as coloring agents.
Y coloring agent: Benzine yellow, quinoline yellow, Hansa yellow
M coloring agent: Rhodamine B, rose Bengal, pigment red
C coloring agent: Phthalocyanine blue, aniline blue, pigment blue
BK coloring agent: Carbon black, aniline black, furnace black, color toner blend
As to each of the above color toners, the light transmittance as a coloring agent is not good and the toner particle shape remains after fixing. Therefore, much of light irradiated to the obtained color image is diffusedly reflected off of the surface and little reflected light is obtained from the color layer, and hence the image is not deep and the color tone reproducibility is not good. Therefore, the image is observed as a flat image.
FIG. 10 shows the status of reflected light when light is irradiated to a color image after conventional fixing. Numeral 1 indicates a transfer material such as paper, 2 a color image, 2C a cyan (C) toner image layer, 2M a magenta (M) toner image layer, and 2Y a yellow (Y) toner image layer. Light 3 is diffusedly reflected off of the Y toner image layer, which is an uppermost layer, like diffusedly reflected light 4 and 3D, and a part of it transmits into the layers, is absorbed by the 2Y, 2M, and 2C layers, and reflected off like 3Y, 3M, and 3C. A color image can be observed by an eye 5 from those reflected lights. In this case, the reflected light from the surface of the uppermost toner layer is intensive and the reflected lights from the inner toner layers are weak. Therefore, the image color tone is not good and a flat and shallow image is obtained.
Therefore, compared with, for example, silver halide color photographs comprising Y, M, and C fine particle dye layers which have superior light transmittance or sublimation heat transfer copies, the image deepness and color tone are extremely inferior.
In view of the above mentioned, Japanese Patent Application Laid-Open Nos. 1988-92964 and 1988-92965 propose a color image forming method which uses a transfer material comprising a base with a white area which is coated with a transparent resin layer.
The first object of the present invention is to provide color images which have the color tone of silver halide photographs and are deep by using the electrophotographic method.
The present invention relates to a color image forming apparatus such as an electrophotographic copying apparatus which forms a copy image which is partially or entirely glossy.
In some of conventional image forming apparatuses such as an electrophotographic copying apparatus, the development conditions are kept constant by using a means for automatically feeding toners (developers) by monitoring the density of each toner, or the development conditions are changed depending on measurement results of the mean density of a document so as to obtain a copy which is faithful to the document as much as possible and can be read easily. However, an apparatus which measures the glossiness of a document during image read and makes a copy image glossy partially or entirely in correspondence with the document according to the measurement results is not realized yet.
Therefore, the conventional image forming apparatus imposes a problem such that a copy of a glossy document is different in feeling from the document because plain paper is used as a transfer material, or the density of characters or the saturation of a color copy decreases due to changing of image data. The gloss of silver halide photographs cannot be reproduced on plain paper, and it is extremely difficult to reproduce a document containing printed, copied, and silver halide images simultaneously.
As to an image recorded on a transparent sheet used for an overhead projector, diffused reflection of the transmitted light can be prevented by making the image surface glossy and a clear projected image with high saturation can be obtained. Therefore, a transferred image with high glossiness is required.
The second object of the present invention is to provide a color image forming apparatus which records a copy image on a transfer material as a glossy image including a portion with no toner image formed, which is not affected by the quality of the transfer material, so as to meet the above demand.
Furthermore, the present invention relates to a color image forming method of an image forming apparatus such as an electrophotographic copying apparatus which makes an image on a transfer material glossy.
The third object of the present invention is to provide a color image forming method which records a copy image on a transfer material as an even and glossy image, which is not affected by the quality of the transfer material, so as to meet the above demand.